A cellular communication device may support several frequency bands, including bands that are referred to as 600 MHz, 700 MHz, 1700/2100 MHz, 1900 MHz, etc. Multiple frequencies are used in each band for multiple RF signals.
When a cellular handset is turned on, it scans available frequencies in each of multiple supported frequency bands to find a satisfactory signal and cell, and to then begin an attach procedure. This involves tuning an RF receiver to each of multiple radio frequencies in turn, and evaluating received signal strengths at each frequency.
A cellular communication device is typically configured to operate within a network of a particular provider, and therefore searches for a signal that corresponds to a cell of the provider. Searching continues until a suitable or acceptable cell is identified. This process can take significant time, during which the device cannot be used for cellular communications.